<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>登陆</title>
</head>
<body>
    <form action="captcha_check.php" method="POST" target="result">
        <img src="captcha.php"  onclick="this.src='captcha.php?'+new Date().getTime();" width="200"><br/>
        <input type="text" name="captcha" placeholder="请输入图片中的验证码"><br/>
        <input type="submit" value="验证">
    </form>
    <iframe name="result"></iframe>
</body>
</html>